This invention relates to apparatus for use in providing signal communication between the interior and the exterior of a pipeline. In the operation of a pipeline, it is frequently important to obtain information as to conditions in the interior of the pipeline. Examples of such applications are: (1) pig signaling devices, that is, devices used to signal the passage of a pig apparatus through the pipeline; (2) corrosion probes, that is, devices to detect and/or measure the rate of corrosion occurring in the pipeline; (3) analysis of the contents flowing through the pipeline such as the amount of water contained in petroleum products or the specific gravity of the products; (4) the temperature of the fluid or gas flowing through the pipeline; (5) the pressure within the pipeline; (6) fluid or gas flow rates; and (7) benchmark systems which may include frequency channels that can be sold to in-line inspection companies.
Others have provided permanently mounted devices for passing a conductor from one side to the other of a pressure bearing wall. For information on how conductors can be extended through a pressure separating wall, see the following U.S. Pat. Nos. 1,541,756; 1,851,939; 1,851,940; 3,135,535; 3,314,030; 3,697,089; 3,772,637; 4,267,401; 4,609,209; 5,235,138 and 5,092,375.
For examples of the use of conductors in pipelines see U.S. Pat. Nos. 4,691,728 and 4,465,104.
These prior art references illustrate and describe various means of passing conductors from one side to another of a pressure barrier. However, none of the references describe a convenient and effective way for providing signal communication between the interior of a pipeline and the exterior arranged so that the instrumentation positioned within a pipeline can be inspected or changed while the pipeline is under pressure. The ability to remove an electrical device, whether signal generating or signal receiving, from the interior of a pipeline and repair or replace it while the pipeline is under pressure can be very valuable to a pipeline operator. This ability reduces the costs that are encountered when it is necessary to depressurize a pipeline in order to provide new or different signal or receiving devices.
Stating it another way, this invention provides an apparatus for conveying signal communication from within to the exterior of the pipeline in a manner that enables the operator of a pipeline to have access to the interior of the pipeline as often as desired and without the necessity to discontinue normal operations of the pipeline.